Fix Issue 3727 (ufuncify + erf)
Staging the infra of a basic PDE Solver
Minor Change
Added util.py- helper functions
Made all changes except ode_order
Improved documentation and cleaned up test failures
3226: give diff a simplify option
Add Sphinx doc building to Travis
Updated sphinx docs
make high-order derivatives simplified by default

Only factor_terms and signsimp are used in the simplification; other
simplification may be possible but that is left for the user
to decide if it's necessary.

* do not simplify in euler_maclaurin

For some reason the size of the derivatives grows if the
simplification is used. I don't know why.
Use an older version of Sphinx, which is known to work

This is to work around https://code.google.com/p/sympy/issues/detail?id=3623.
Echo each command from test_travis.sh
Implemented TODO's
Add missing with_statement imports (issue 3751)
[integrals/meijerint] Fix a bug in _split_mul.

This fixes issue 3761.

_split_mul tries to write an integrand as c*x**a*f, where a and c are
independent of x. However, it did not actually test that a is independent
of x ...

Fix this, and add the test from the issue.
Merge pull request #2012 from skirpichev/3751-with-import

Add missing with_statement imports (issue 3751)
3717: Factors cleanup and non-integer exponent handling

I tried removing I altogether from the factors, storing it as
-1**(1/2) but then there were transform tests that failed.

denominators of Rationals are given a negative exponent. This is
not done with Expr factors -- this is not suppose to be handling
rational expressions, really.
handle 1.0 and clarify div, normal, quo, rem

- core/basic.py
    sympy typo
- core.expr.py
    args_cnc splits -1 from 1.0, too
- core.exprtools.py
    o sympify Python numbers
    o be more careful with 1.0 so Float expr doesn't become Rational
        e.g. Float(1.0)*x != x
    o rework the handling of canonicalization
    o updated the docstrings of div and normal to highlight their
      similarities and differences
    o remove the powdenesting during division; Factors is suppose to
      be fairly naive and fast
    o rem no longer returns 0 when other is contained in self; it
      is somewhat minamed because div is not really doing a divmod
      calculation, it is doing division, removing common factors
      from self and other: a*b*c/b -> a*c/1
handle constant term during div or normal
process +/-1; allow any SYMPY_INT